1. Field of the Invention
The present invention relates to a plasma processing apparatus and a plasma processing method for performing various plasma processing for film formation, an etching, etc. through a gas phase reaction, and more particularly to a plasma processing apparatus and a method for performing various plasma processing for film formation, a surface treatment, etc. on a tape-shaped or film-shaped substrate such as a magnetic tape.
2. Description of Related Art
There has been hitherto known a technique for forming a carbon film or the like as a protection film on the surface of a tape-shaped or film-shaped substrate such as a magnetic tape or the like. FIG. 1 shows one of apparatuses which are capable of implementing such a technique.
The apparatus shown in FIG. 1 includes a cylindrical can roll 103, a tape-shaped or film-shaped substrate 115 which is fed by rotation of the can roll 103, a flat plate electrode 300 which is disposed to face the can roll 103, and a high-frequency power source 108 for supplying a high-frequency power to the flat electrode 300 through a matching box 107 and a blocking capacitor 106. In the following description, the can roll is referred to as "one electrode", and the flat plate electrode is referred to as "the other (or counter) electrode". The substrate 115 is fed out from a feed-out roller 113 through a guide roller 104 to the can roll 103, and then a carbon film (coating) is formed on the substrate 115 by a high-frequency discharge which is induced in a gap between the can roll 103 and the flat electrode 300. Raw gas is supplied from a gas supply system 102, and hydrocarbon gas such as ethylene or the like may be used as the raw gas to form a carbon film.
The substrate 115 on which the film formation is completed is fed through a guide roller 104 and taken up by a take-up roller 114. The film forming operation of the carbon film on the surface of the substrate 115 is continuously performed while feeding the substrate. In the apparatus shown in FIG. 1, a feed-out chamber 111 in which the feed-out roller 113 is disposed and a take-up chamber 112 in which the take-up roller 114 is disposed are kept in an atmospheric state, and a film forming chamber 101 in which the film formation is performed is kept in a pressure-reduced state. Therefore, a buffer chamber 110 is provided between the film forming chamber 101 and each of the feed-out chamber 111 and the take-up chamber 112 to thereby constitute a differential exhaust system. Normal stainless steel or aluminum is used as a component for the chamber 100. The apparatus further includes an exhaust pump 109 for exhausting gas from the film forming chamber 101, and exhaust pumps 116 for exhausting gas from the buffer chambers 110.
The can roll 103 constituting the one electrode has a cylindrical body which is elongated in the vertical direction on the surface of the drawing, and it is grounded. That is, the flat electrode 300 serves as a cathode electrode and the can roll 103 serves as an anode electrode.
When a longitudinal substrate such as a magnetic tape or the like is used as the substrate 115 in the apparatus as shown in FIG. 1, the feeding speed of the substrate is required to be as high as possible in order to improve its productivity. However, when the feeding speed of the substrate 115 is increased, the thickness of a film formed on the substrate 115 becomes smaller. In addition, when a carbon film or the like is used as the surface protection film, there occurs a problem in its adhesiveness to the substrate.